This is where the hoaxers, frauds and mountebanks swoop in. There’s glory to be had in going where people haven’t gone before and doing what they think impossible, and where there’s glory, there’s often money.

Take the once-celebrated “Nature Man” Joe Knowles for example. In 1913, at a time when Americans were growing increasingly distant from nature, this Boston artist proposed to the struggling Boston Post that he disappear naked into the Maine woods and survive by wits alone. He’d slip them “dispatches” written on birch bark, and the paper would publish them to boost sales. The stunt worked: Knowles became famous and spun a lucrative career in showbusiness out of the experience, and the paper started selling like hot cakes. It was only through the sleuthing of a rival paper that the truth came out. He’d faked the whole thing.

Generally speaking, the more celebrated the feat, the fewer people there are to bear witness.

This is especially true of polar exploration. American Naval engineer Robert Peary has gone down in history for his polar expeditions, and is still widely credited with being the first to reach the North Pole. By April of 1909, when he finally claimed to have reached the pole, his party was down to six people: himself, his “valet,” Matthew Henson, and four Inuit guides. Of that group, only Peary knew how to navigate, and it’s his account that modern historians rely on—and don’t particularly trust.